This paper reports progress on Mitsubishi’s first commercial introductions of the M501G1 and M701G2 gas turbines for 60Hz and 50Hz, respectively. The first fire of the 50 Hz gas turbine took place late 2006 at Tokyo Electric Power Company’s (TEPCO’s) Kawasaki Thermal Power Station in Japan, and the 60 Hz unit in January 2007 at Portland General Electric’s Port Westward power plant at Portland, Oregon in the USA. The M501G1 and M701G2 gas turbines are upgrades to Mitsubishi G-series technology that was first introduced a decade ago utilizing steam from the bottoming cycle to cool the combustion liner, instead of compressor discharge air. In the abovementioned upgrades steam-cooling application is now extended to cool the turbine blade-rings thereby enabling better blade tip clearance control particularly during start-up transient conditions. It additionally benefits performance and reliability. Upgrades were also made to the row 1 and 2 vanes and row 1 blades utilizing advances in design technology since the original introduction of the G-series in 1997. Long-term reliability verification testing of the M501G1 gas turbine has been continuing at the Mitsubishi’s T-Point combined cycle power plant located at Takasago, Japan, since May 2003. This paper provides an update of that upgraded gas turbine with over three years of operating experience.